diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index c0a673860..898784013 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -50,6 +50,7 @@ struct psa_hash_operation_s
     psa_algorithm_t alg;
     union
     {
+        unsigned dummy; /* Make the union non-empty even with no supported algorithms. */
 #if defined(MBEDTLS_MD2_C)
         mbedtls_md2_context md2;
 #endif
@@ -84,6 +85,7 @@ struct psa_mac_operation_s
     uint8_t mac_size;
     union
     {
+        unsigned dummy; /* Make the union non-empty even with no supported algorithms. */
 #if defined(MBEDTLS_MD_C)
         mbedtls_md_context_t hmac;
 #endif
@@ -102,6 +104,7 @@ struct psa_cipher_operation_s
     uint8_t block_size;
     union
     {
+        unsigned dummy; /* Make the union non-empty even with no supported algorithms. */
     } ctx;
 };
 
@@ -115,6 +118,7 @@ struct psa_aead_operation_s
     uint8_t block_size;
     union
     {
+        unsigned dummy; /* Make the union non-empty even with no supported algorithms. */
     } ctx;
 };